Colloids and Surfaces C: Environmental Aspects最新文献

Bio-based surfactants have garnered significant interest nowadays in wide applications particularly in the oil recovery field owing to their renewable property, outstanding surface/interface activity and eco-friendliness. The ultra-low interfacial tension between crude oil and brine is one of the key parameters for evaluating surfactants used in enhanced oil recovery. In this study, we developed a new binary surfactant system formulated by a bio-based zwitterionic surfactant (POA) and a bio-based nonionic surfactant (SOG), and the binary surfactant system exhibits a strong interfacial activity at a very low surfactant dosage. With the total surfactant concertation in a range of 0.1–3 g/L and the mass ratio of POA to SOG in a range of 5:5–9:1, the interfacial tensions of the binary system between crude oil and simulated formation brine could be significantly reduced to an ultra-low level (∼10⁻³ mN/m), indicating a strong synergistic effect between molecules in the binary system. Meanwhile, with the total surfactant concertation of 0.5 g/L and the mass ratio of POA to SOG of 7:3, the binary system demonstrates ultra-low interfacial tensions (∼10⁻³ mN/m) between crude oil and simulated formation brine at the temperature up to 80 ℃, NaCl up to 75 g/L and Ca²⁺ ions up to 20,000 mg/L, and the emulsification and oil film peeling ability are also improved compared with those of the individual POA and SOG. This study opens a new window for the binary bio-based surfactants and provides insights in designing and optimizing the cost-effective displacement systems for enhanced oil recovery with ensuring environmental sustainability.

Potassium-type zeolite (KZ) was prepared from coal fly ash by hydrothermal activation treatment using potassium hydroxide solution and potassium-type fine-grained zeolite was prepared by dry milling (KZ-D) or wet milling (KZ-W). The effects of the different treatments on the Pb²⁺ adsorption performance were assessed. KZ-W resulted in a much smaller particle diameter (0.61 ± 0.12 µm) than KZ-D (1.4 ± 0.48 µm) and KZ (6.5 ± 0.49 µm). KZ-W also realized a higher pore volume, mean pore diameter, and specific surface area, than KZ-D and KZ. Additionally, KZ-W realized a greater Pb²⁺ adsorption capacity (242.6 mg/g) than KZ (195.3 mg/g) or KZ-D (188.9 mg/g). The adsorption phenomena were fitted to the Freundlich and Langmuir models to clarify the Pb²⁺ adsorption mechanism, and then both models showed a good fit to the experimental data (the correlation coefficients of 0.914–0.996 for Freundlich model and 0.897–0.981 for Langmuir model). Additionally, the ion exchange capability, elemental distribution, and binding energy before and after adsorption were analyzed. The results indicated that the physicochemical characteristics of the tested adsorbent surface affected the Pb²⁺ adsorption capacity in the aqueous phase. According to kinetics, the pseudo-second-order model matched the experimental data (the correlation coefficients of 0.996–0.999). The samples also demonstrated selective adsorption of Pb²⁺ in a binary solution. The results demonstrated that KZ-W can effectively remove Pb²⁺ from the aqueous phase and that it may be a useful tool for preventing contamination of water bodies.

In this research article, we have performed the degradation of methylene blue dye (MB) in the presence of ZnFe₂O₄/Ag₂WO₄ photocatalyst. These catalyst materials are prepared by a simple combustion method followed by a solution mixing method. The structure and morphology of prepared composite material are analyzed by using XRD, FTIR, UV-DRS, and scanning electron microscopy. The antimicrobial property of composite material is studied against E. coli and S. aureus food pathogenic bacteria. After the incubation time, the antimicrobial activity of the composite material shows a clear zone of inhibition. This composite photocatalyst is a promising material to increase the degradation percentage of MB (Methylene blue) dye in the presence of UV light. ZnFe₂O₄/Ag₂WO₄ composite material shows 72.72% degradation of the MB dye. The photocatalytic activity of composite material has been performed by varying the catalyst dosage and pH level of the medium used for the degradation process. The role of composite material in the degradation of dye and their increase in the reaction rate has also been discussed. From these results, the ZnFe₂O₄/Ag₂WO₄ composite is a good material to degrade the toxic pollutants in the environment.

Development of high-performance hydrophobic layer using green and economic method is still urgently on demand for wide applications of membrane distillation (MD). In this study, a novel Janus membrane was prepared by electrospinning polystyrene with the water addition on the surface of hydrophilic electrospun nanofiber substrate. With increasing water content to 3 wt%, the hydrophobic layer is completely converted to be nanofiber-dominate morphology that could be beneficial for water vapor permeation during MD process. The surface roughness, water contact angle value and porosity of the hydrophobic layer are enhanced by the water addition, and the optimized Janus membrane with the hydrophobic layer prepared at the water content of 2 wt% could achieve a high water flux of 33.1 L/m²h and superior salt rejection of >99.9 % when 3.5 wt% NaCl solution was used as the feed solution. The as-prepared Janus membrane shows better performance stability and reusability than the control membrane (without the water addition) within the 24-h continuous operation duration. Our work demonstrates that the proper water addition could be used as a green strategy for fabricating efficient electrospun nanofiber membranes for the direct contact membrane distillation (DCMD) processes.

The highly efficient and recoverable magnetic hydrothermal biochar (β-CD@MHBC) was prepared by combining red sandalwood and β-cyclodextrin, and was used for removing methylene blue (MB) and auramine O (AO) dyes in the single and binary systems. The physical and chemical properties of the β-CD@MHBC were characterized using SEM-EDS, BET, XRD, VSM, FT-IR, and XPS techniques. Batch adsorption studies revealed that the obtained maximum adsorption capacities of β-CD@MHBC for MB and AO in the single system were 303.1 and 400.0 mg g⁻¹, while in the binary system were 151.1 and 169.1 mg g⁻¹ under the optimal conditions of pH 6, 1.0 g L⁻¹ dosage, 150 mg L⁻¹ dye concentration and adsorption time of 180 min, indicating the presence of competitive adsorption with AO possessing stronger affinity in the binary system. The adsorption behaviors of MB and AO could be well described by the Langmuir isotherm model and pseudo-second-order kinetic model in both single and binary systems. The possible adsorption mechanism involved pore filling, electrostatic attraction and hydrogen bonds between β-CD@MHBC and dye molecules. Furthermore, the spent β-CD@MHBC displayed excellent reusability and stability with removal efficiencies of 94 % for MB and 83 % for AO after five cycles of adsorption-desorption. In summary, the prepared β-CD@MHBC with excellent adsorption property and regeneration performance could have great potential for continuous removal of target pollutants in actual wastewater treatment.

Fast removal of emerging organic pollutants (EOPs) is very important for the remediation of the water environment. Therefore, in this study, we used a simple grinding-calcined assembly method to prepare CoFe@TiN metallic composite, which possessed superb peroxy disulfate (PDS) activation ability with efficient pollutant degradation and excellent cyclic utilization. Rhodamine B, a highly representative and extensively used EOP, was adopted as a model pollutant, showing that it was completely degraded within only 9 min by the CoFe@TiN/PDS. During the degradation, superoxide radical (O₂^•−) were the main active oxygen species responsible for pollutant degradation. Further analysis showed that the synergistic effect of Fe(III)/Co(II) effectively activated the PDS to degrade the pollutant. In practical applications, the CoFe@TiN/PDS system can resist the influence of complex matrix in water and effectively remove EOPs in real water bodies. This study comprehensively evaluates the ability of the CoFe@TiN/PDS system to remove EOPs and thus provides a new scenario or pathway for the removal of EOPs in real contaminated water bodies.

Zeolitic imidazolate framework (ZIF)-8 nanoparticles demonstrate excellent physicochemical properties, which make them suitable for a variety of applications. However, their scale-up manufacturing requires insight into the rate of addition of precursors. This study investigates the impact of Zn salt precursor rate of addition to an organic linker solution on the morphology and size of ZIF-8 nanoparticles, and their potential for the adsorptive removal of dyes (cationic and anionic). ZIF-8 nanoparticles were produced with a molar ratio of Zn/2-methyl imidazole (Hmim)/H₂O at 1/36/2206 by varying the flow rate of Zn precursor at 5, 10, 15, 20, and 25 mL/min into the Hmim solution. The physicochemical properties of the synthesized ZIF-8 nanoparticles were assessed using microscopy, analytical, and spectroscopy techniques. Owing to different flow rates of the precursor, variations in the ZIF-8 particles’ size and morphology were observed. It was found that the optimum flow rate was 15 mL/min (named Z-15), resulting in particle size of 261 nm, with a high specific surface area, thermal stability, and a substantially high yield of ∼89%. Furthermore, the dye adsorption studies, performed using Z-15 NPs, resulted in high methylene blue (∼82%) and methyl orange (∼76%) removal efficiency. The adsorption performance was maintained with dye-spiked simulated wastewater. The superior dye adsorption capacity of the ZIF-8 nanoparticles could be attributed to their microporous characteristics. Thus, this study demonstrates that the rate of addition of Zn precursor in the synthesis of ZIF-8, indeed, affects both their morphology and size, and the resulting nanoparticles exhibit promising adsorption performance toward dyes.

Chromium contamination due to industrial effluents has been recognized as one of the major problems since chromium compounds affect human health leading to adverse health effects of humans. Among many adsorbents that have been experimented with, cellulose fibers have been identified to be very effective for chromium removal. Agave americana, a plant native to Central America, is rich in cellulose fibers, which consist of esters, ethers of alcohol derivatives of cellulose showing coordinating ability toward heavy metal ions. This study is aimed at optimization of solution parameters, such as shaking time, settling time, solution pH and adsorbent dosage, while varying one parameter at a time throughout a broad range keeping others constant, for most efficient adsorption of Cr(III) species, followed by investigation of equilibrium and kinetics aspects under optimized conditions. Adsorption of Cr(III) from solutions of different concentrations on untreated AAF fulfills the requirements of the Langmuir adsorption isotherm at equilibrium which is probably due to the fine fibrous nature of the biosorbent. Moreover, the extent of Cr(III) on Agave americana fiber (AAF), investigated during the early stages of adsorption, leads to the validity of the pseudo first-order kinetics with a relatively high regression coefficient. Although untreated AAF shows a strong affinity toward Cr(III), its adsorption ability toward Cr(VI) is undetectable, suggesting that surface modification of AAF be performed. In this context, EDTA-treated AAF demonstrates a significant improvement on Cr(VI) removal, indicating the possibility of extending the present investigation for removal of chromium species under industrial setting.